The hearing was originally set for May 30, but both prosecutors and Tsarnaev's defense attorneys requested earlier this week that it be pushed back to July 2, so they would have more time to gather and review evidence.

Three people were killed and 264 others wounded when Tsarnaev, 19, and his 26-year-old brother, Tamerlan, allegedly detonated bombs made from pressure cookers on April 15, near the marathon finish line on Boylston Street.

The brothers are also accused of killing an MIT police officer three nights later and leading police on a chase to Watertown.

The pursuit ended with Tamerlan Tsarnaev dead after a shootout with law enforcement officers.

The younger Tsarnaev was wounded in the exchange and captured the next day after a day-long manhunt that virtually shut down the Boston area.

He is being held at a federal prison hospital at Ft. Devens, charged with using a weapon of mass destruction. If convicted, Tsarnaev could receive the death penalty.

Meantime, Homeland Security Secretary Janet Napolitano will be in Boston Friday to discuss the marathon bombing with local officials.

A DHS statement said Napolitano also plans to speak with law enforcement officers and other first responders, "to reiterate the Department’s on-going support and collaboration on issues including training and preparedness, as well as the need for continued information sharing at all levels of government to enhance public safety."

Before leaving the city, Napolitano will visit the Stephen M. Lawlor Medical Intelligence Center -- a unit of Boston's Emergency Medical Services which played a key role after the explosions -- and pay tribute to the bombing victims at the memorial in Copley Square.